Apparatus for transmitting mechanical vibrations



March 4, 1958 DE'VRIEs 2,825,763

APPARATUS FOR TRANSMITTING MECHANICAL VIBRATIONS Filed Feb. 16, 1955 IN V EN TOR.

' Mgcla ez cZe l/rL'es I Affyd.

llnited States 1 atom APPARATUS FOR TRANSMITTING MECHANICAL VIBRATIONS Machiel de Vries, Amsterdam, Netherlands Application February 16, 1953, Serial No. 337,149

Claims priority, application Netherlands May'26,.1952

10 Claims. (Cl. 179-40041) The present invention relates to apparatus for transmitting mechanical vibrations, and may'comprise, for :example, part of an acoustic device.

The invention is more particularly concerned with a gramophone pick-up, such as of the piezo-electric type, and the invention will therefore be described in connection with such devices.

In gramophone disc recording, the constant velocity principle is usually applied, i. e. a constant sound intensity is recorded on the disc with an amplitude which is inversely proportional to the frequency, so that the velocity at which the position of equilibrium is passed is constant for all frequencies. If an electromagnetic pick-up is used for reproducing the record, in which pick-up the generated voltage is obtained by induction, such voltage will increase in direct proportion to the frequency, ifthe amplitude of the needle movement is constant.

If, however, this amplitude is not constant, but inversely proportional to the frequency, the voltage will become constant at a varying frequency. This can also be understood by bearing in mind that the induced voltage is determined by the velocity, which, in a constant-veloc ity system, is kept constant, independently of the frequency.

If, however, the voltage is generated piezo-electrically, it is directly proportional to the amplitude. When playing a record of the type indicated above, the voltage decreases as the frequency increases, since the amplitude of the needle movement decreases as the frequency increases.

The object of this invention is to provide a coupling between the needle which follows the groove of the record and the crystalgenerating the piezo-electric voltage, the coupling being arranged to become closer as the frequency increases, in such a-manner that, when the needle amplitude changes in inverse proportion to the frequency, in accordance with the constant velocity system, the piezoelectrically generated voltage remains constant, i. e. the output remains independent of thefrequency.

Another object of the invention is to reduce the fragility of such transmitting apparatus, so that its mounting. can therefore be efiected better and more quickly.

A further object of the invention is to limit the mass of the moving parts of the apparatus as much as possible and to give said parts such a shape that natural vibrations within the frequency range used are avoided.

According to the invention, in apparatus fortransmitting mechanical vibrations, comprising at leastone vibradon-supplying element and a vibration-receiving element, such elements are coupled together by a coupling body of a material, with plastic properties, such as e. g. polyvinylchloride, which at low vibration frequencies behaves like a viscous mass and hence tends to damp the vibrations, but which, at high frequencies, behaves like a harder material and provides a more firm coupling between said elements.

This change of elasticity of the coupling body with the change of the frequency can be such that a perfectly ice and also in order to prevent any movement of the needle in the longitudinal direction of the sound track, the needle is preferably mounted on a metallic strip, which engages the narrower end of the coupling body by means of two lugs arranged on either side of the strip, whereas the other-end of said strip is secured e. g. to a holder for the crystal.

Movement in the longitudinal direction of the strip is prevented by this means. By deforming the strip overa "portion of its length, so that, looking in the longitudinal direction of the strip, said portion is at right angles thereto, the strip-becomes "flexible in its own plane for permitting the needle to perform an oscillatory movement.

in apparatus of the turnover type having a coarser needle for ordinary records and-a finer needle for microgroove records, this construction offers the particular advantage that the inoperative needle does not exert a disturbing-influence and does not produce undesirable vibrations. This'is'due to itsslight mass and the'slight mass of the part of the coupling body connected therewith, so that no irregularities occur in theflat voltagefrequency curve.

The invention will now be described with reference to the accompanying drawing showing an embodiment of a pick-up provided with a piezoelectric crystal'and with two needles, either of which as desired can be brought rapidly into the operative position 'by turning the apparatus through in its holder.

Figure 1 shows a cross-section through the apparatus, whereas Figure 2 shows an exploded view of the apparatus in perspective. The reference numerals'designating the various parts are the same in the two figures.

Reference numeral 1 designates a crystal, one end of which is clamped between two blocks 2 and 2a. The terminals in contact with the crystal 1 are not shown.

At the other end of the crystal, a coupling body 3 is provided, which has the shape of a block of flat material as shown in Figure 2 and has its broadest portion provided with-a slot for receiving said other end of the crystaljl therein. The coupling body'3 consists of plastic, elasticaily deformable "material which weakly transmits low frequency vibrations, but which with increasing frequency behaves as a material that becomes firmer and firmer, so that it transmits higher frequencies more intensively. The coupling body 3 therefore causes a loose coupling at low frequencies and a more firm coupling at rower ends of the'coupling body 3,.but by means of an interchangeable .needle holder 5 and '5a respectively. Each needle holder 5 and'Sa consists of ..a metallic strip having one end screwed to the associated clampingbIQck 2 or 2a by a screw 6 or 6a, while at the other end it engages a narrow end of the coupling body 3 with two bent lugs 7 for transmitting to said body 3 vibrations directed at right angles to the longitudinal direction of the needle holder 5 or St: and located in the plane thereof. In an opening in each needle holder 5 or 5a, the associated sapphire 4 or 4a is secured.

In order to enable the particular sapphire 4 or 4a not engaging the groove of a gramophone record being rethe parts. a a a V offthe element;

produced to perform an oscillatory movement, a portion of each needle holder or 5a is deformed as at 8 to lie substantially at right angles to the plane of the strip, so

7 that the needle holder 5 or 5a is rendered flexible about 'a line substantially at right angles to the plane of the strip, so that-the sapphire 4 or 4a can perform an oscillatory movement in a direction normal to its axis and at right angles to the longitudinal direction of the needle holder 5 or; So, while undesirable movements of the sapphire 4 or 4a in the longitudinal direction of the needle holder 5 or 5a are suppressed. The needle holder 5 or 5a reinforces the transmitting apparatus, prevents undesirable movements of the sapphire 4 or 4a and is readily interchangeable. 7 v a V 7 It will be clear that it is the great deformability of the coupling body 3 whichprotects the apparatus against breakage and damage, during use as well as assembly,

'and that the construction for connecting the e needle holder and the crystal is very simple, which is of particular importance in view of the small dimensions of a The coupling body 3 has the additional valuable char- ,acteristics for use in hi-fidelity reproduction of resistance '10 aging, as well as thermal stability. Resistance to aging'means that polyvinylchlorides and their equivalents do not lose their desired physical properties within the normallife of a cartridge'of this type. 'Compare, for

example, the brittleness acquired by rubber after a comparatively short time. 'Ihat polyvinyl chloride is unaffected by aging is established in. the Handbook of Plastics, authored by Herbert R. Simonds and Carlton Ellis, published by .D. Van Nostrand Company, Inc.,

-to a limited extent and high 3. A piezoelectric pick-up including a piezoelectric element and two gramophone stylus holders, said ele ment and each of said stylus holders mounted by one end thereof 'in the pick-up, .a coupling body, comprising a single block of material'engaging the other end of each stylus holder and the other end of the piezo- 7 thermal stabilityin the range of 327-120 F., and of damping low frequency vibrations to a limited extent and damping higher frequency vibrations to a lesser extent,

6. A phonograph .pickeup element comprising, a support, a piezoelectric element mounted atone end to said support, a stylus, and means coupling said stylus to said element, said. coupling element having the characteristics of resistance to aging, thermal stability in the range of,

.32-120? F., and of damping low frequency vibrations frequency vibrations to a' lesser extent; r l

7. A phonograph'pick-up comprising, a support, a V

piezoelectric element mounted at one end in said support, a coupling member fixed to the other end of said element, and having an end portion projecting from said Second Printing. Thermal stability as used'herein means the property of substantially retaining the physical char- ,acteristics of the material-Within a range of temperatures between. 32Yand 120 F., the range'within which the pick-up is likely to be used. See Wakeman, Chemistry {of Commercial Plastics published by Reinhold in 1947.

Comparison of pages 321 and540 demonstrates that chloride in the range of 32 to 120 F; 'It is remarkable that the voltage-frequency curve for records of the constant velocity type is perfectly flat when the pick-up according to the invention is used and that this curve does 'not show any irregularities.

This is to an appreciable extent due'to the slight inert rubber elongates almost ten times as much as polyvinyl :mass of the moving part of the apparatus not inuse.

I claim: I V 1. .A piezoelectric pick-up including a piezoelectric V element .and two gramophone stylus holders, said elemer t and 'each of said stylusholders mounted by one end thereof in the pick-up, a coupling body, comprising a single block of plastic elastic-material engaging the other end of each stylus holder and the other end of the :piezoelectricelement, thecoupling body serving as the sole. coupling means between the 'styli, and the other end of the element. V a 2. A piezoelectric pick-up including a piezoelectric element and two gramophone stylus holders said ele-,.

ment and each of said stylus holders mounted by one 7 end thereof in the pick-up, -a;coupling body, comprising a single block of polyvinyl chloride engaging the 'otherend of each stylus holder and the other end of the piezoelectric'element, thecoupling body serving as the sole coupling 'rneans betweenthe styli and the other end element, and ,a resilient stylus holder connected at one end to said supportand carrying a stylus .at the other end, said other, end of said stylus holder detachablybearing against said coupler. r

8. A pick-up according to claim 7 in which said holder is detachably mounted to said support.

9. A phonograph pick-up as set forth in claim 7 where-' in the stylus holder engaging said end portion is pro vided with tabs extending from .said holder and detach ably embracing the sides of said projecting end portion;

10. A phonographic pick-up comprising, a support, an 7 elongated fiat piezoelectric element fixed atone end'in .said support, a plastic coupling member having acen- .trally located slot corresponding to the, cross sectional configuration of said element and having at least one tapered end'portion extending away from said slot, the .free end of said element being inserted in said slot, at least one stylus mount, said stylus mount being fixed at one end to said'support and having a stylus at the other endthereof, the other end of said stylus mount embracing said coupling member at the tapered end thereof. References Cited in the file of this patent V UNITED STATES PATENTS 1,977,433

Dunning Oct. 15, 1934 2,328,952 Burt Sept. 7, 1943 2,480,907 Dally Sept. 6, 1949 2,492,446 Schumann Dec. 27,1949 2,567,105 Dreisbach Sept. 4, 1951 2,639,156 Ward May'19, 1953 7 2,689,738 Jensen, Sept. 21, 1954 2,703,343 Shepvangers Mar. 1, 1955 2,816,056 Harris Dec. 10, 19. 57

U. S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE GF CORRECTION Patent No, 2,825,763 March 4, 1958 Machiel de Vries It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as oorreoted below,

Column 2, line '71, after "4a" strike out "not".

Signed and sealed this 29th day of April 1958.,

(SEAL) Attest:

KARL Ho LINE ROBERT c. WATSON attesting Officer Comnissioner of Patenta 

